Authentication and other security issues are currently areas of extensive research and development, both theoretical and practical. One field of endeavor is the authentication of data on a DVD or comparable technology, which may or may not include CDs and new DVD technologies, but is typically applicable across DVD technologies due to the similarities between DVD technologies. With DVDs, CDs, and other freely distributable media disks, the authentication has to be particularly strong (e.g., use a cryptographic method).
Disk-based media are typically block-based devices. So the access time of block data and the computation time of any cryptographic algorithm used should meet the specifications of a system on which the disk-based media are used. Moreover, the contents could sometimes be encrypted for secrecy. Other considerations for secure device secrecy and authenticity techniques for disk-based media include that the technique should support a read-only medium, should support mass production of disks (not requiring custom or unique data on each disk), and the additional data stored on the disk for authentication should only impose a reasonable overhead.
Some efforts to meet these requirements have been proposed, but, as is the case with many solutions in secrecy and authentication techniques, there is room for improvement. For example, one could attach a block signature based on public key cryptography (example, RSA signature), but this is relatively slow since every block of data that is read would require an RSA signature calculation. Besides, the size of an RSA signature for every block would impose a relatively high overhead. As another example, one could attach a SHA hash (or equivalent) for every block written in a custom protected area of disk, but this would require the manufacture of custom disks. As another example, one could attach a secret-key based message authentication code such as HMAC (or equivalent) for each block, but if the HMAC has to be the same for all disks, this becomes a common secret key mechanism, which may not provide a desired level of security. As another example, one could use a hierarchical signature approach that requires multiple seeks of the block device for every block access, to read the members of the hierarchy, but this may lead to increased latency.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.